I am using MyEclipse 6.6.0. and Spket IDE 1.6.17.
(I noticed in my product configuration there is Xerces for Spket IDE 2.8.0 - not sure where that came from).

When I add a new .js file the code completion works.

When I edit an existing .js file from my project that is (using Spket Javascript Editor btw) code completion never shows up. I am tied to the ClearCase plugin as well. But I believe that has nothing to do with it.